More carbon dioxide could lead to improved growth rates and water efficiency for some crops. Currently resource-poor areas could grow new crops.
The warmer winters could lead to less sickness in winter and less power used to heat homes.
Overall, the report said: "We are not in a position yet to estimate whether climate change might bring a net cost or benefit to New Zealand in the near future, and at what specific point positive impacts could turn negative.
"Many issues are still unexplored or poorly understood. However ... [in the long term] if climate change continues unabated, there is little question that the global economy and human welfare would be put under substantial threat."
Pete Hodgson, the minister responsible for co-coordinating the Government's work on climate change, said the issue required a response. Every aspect of New Zealand life would be affected in one way or another.
Green Party co-leader Jeanette Fitzsimons said the report showed that even if greenhouse gas emissions were reduced "our unsustainable energy use has had a permanent impact on the environment which will affect all future generations."
Ms Fitzsimons also welcomed the Government underlining its commitment to the Kyoto Protocol.
The international agreement binds developed nations to cutting greenhouse emissions to 1990 levels by 2012.
But Act MP Gerry Eckhoff said: "Attempting to halt natural changes in the planet's climate is pointless and absurd.
"Global warming is an invention that creates jobs for pseudo-scientists who fancy a career in abstract projections of the inevitable."
As emissions rise, the Government is still working through how to implement the Kyoto Protocol.
The report predicts temperatures to rise more quickly in the North Island than the South Island, but generally less than the world average.
It will rain more in the west and less in the east. The climate generally will be dominated by extreme events with less frost in winter and hotter summer days.
While global sea levels are expected to rise by between 9cm and 88cm by 2100, experts say the effect on New Zealand is hard to predict.
The report says earthquakes and changing sea patterns will havemore influence than climate change.
Changing temperatures mean crops grown only in the north will be able to move south.
- NZPA
www.nzherald.co.nz/climate
Intergovernmental Panel on Climate Change (IPCC)
United Nations Environment Program
World Meteorological Organisation
Framework Convention on Climate Change
Executive summary: Climate change impacts on NZ
IPCC Summary: Climate Change 2001
